The invention relates to a communication system, particularly for a motor vehicle.
The so-called FlexRay standard (“FlexRay”) is currently establishing itself for the data transmission between motor vehicle control units, which standard is described by a preset protocol specification.
FlexRay has the purpose of meeting the increased demands of future networking in the vehicle, particularly a higher data transmission rate, a real-time capability and a fail-safe capacity. However, the current focus is primarily on the higher data rate which is necessary today as a result of the continuous increase of distributed applications, such as driver assistance systems, in premium vehicles.
In order to operate a FlexRay network node, such as a control unit, on a FlexRay bus, as a rule, two components are used: the bus transceiver and the communication controller. The bus transceiver establishes the direct connection to the data line: on the one hand, it writes the logical information, which is to be sent, in the form of voltage pulses onto the bus; on the other hand, it reads out the signals which are sent by other users on the bus. This layer is called a physical bit transfer layer or physical layer.
In addition, the FlexRay standard includes the bus protocol. The bus protocol controls how a network starts, how bus timing is established and which control units are permitted to send at which point-in-time. The communication controller converts the bus protocol in each control unit. It, for example, packages the information to be transmitted in a data packet and, at the correct point in time, transfers this data packet to the bus transceiver for transmission.
The Internet Protocol (IP) is a network protocol that is widespread in computer networks. It is a (or the) implementation of the Internet layer of the TCP/IP reference model or of the network layer of the OSI reference model. The IP forms the first layer of the Internet protocol family that is independent of the transmission medium. An IP address (Internet protocol address) is used for the unambiguous addressing of computers and other devices in an IP network.
Communication systems are known which include a media access control layer (MAC layer) by which the access to the transmission medium is controlled and by which, for example, multiplex processes can be controlled.
In addition, a media-independent interface (MII) is known and standardized by which a media access layer, particularly an Ethernet layer or data packets provided in the Ethernet data packet format, can be converted onto a physical layer.
It is now an object of the invention to specify a communication system that is improved with respect to the prior art.
A communication system according to the invention comprises a plurality of FlexRay network nodes by which respective data packets in an IP data packet format or Ethernet data packet format are provided, particularly are generated, transmitted, temporarily stored and/or modified. The IP data packet format or the Ethernet data packet format each has a plurality of bit positions which are provided for the transmission of preset types of information. By way of the physical layer of a FlexRay bus system, data are transmitted between the FlexRay network nodes. The FlexRay network nodes each comprise a software-type and/or hardware-type media access layer (MAC) which is set up such that the data packets provided in an IP data packet format or Ethernet data packet format are converted to a preset media-independent data format (in the following, also called data packet format) which is preset particularly by the so-called MII (media independent interface) standard or a standard (for example, the RMII, SMII, SMII, etc.) derived therefrom or based thereon. The FlexRay network nodes each comprise a software-type or hardware-type adaptation layer which is set up such that the data provided in the media-independent data format, particularly data packets, are converted onto corresponding signals of the physical layer of the FlexRay bus system.
In this case, preferably before a conversion onto the preset signals of the physical layer of the FlexRay bus system, the data packets or data are not converted or packaged into FlexRay data frames. A FlexRay network node according to the invention therefore preferably differs from a conventional FlexRay network node in that, by means of it, data packages are provided in an IP data packet format or an Ethernet data packet format, and in that—without a temporary storage in the form of FlexRay data frames (with a corresponding preset data format)—these are imaged by way of a correspondingly set-up media access layer on the physical layer of the FlexRay bus system (FRG) which is known per se and preset, particularly standardized. By the use of a media access layer (MAC), which is known per se, is well tested, and widely used, together with the use of a media-independent data format associated therewith and also known per se and well tested, the IP or Ethernet technology can be combined in a reliable manner and at low expenditures with the FlexRay Technology known per se from the motor vehicle field.
As a result, it is achieved that IP data packets or Ethernet data packets, which may originate from a plurality of known program-related or hardware-related devices, can be transmitted by way of a proven suitable physical layer which was tested particularly for motor-vehicle-related environments. Because of the fact that the rigid logical framing of the FlexRay bus system is not applied, which framing is determined essentially by the FlexRay data frame structure and the FlexRay time slot structure, but instead IP data packets and Ethernet data packets are imaged indirectly by way of the media-independent layer, particularly the MII layer, onto the physical layer, the flexibility advantages and cost advantages of the IP/Ethernet technology can be combined with the advantages of the FlexRay technology. On the whole, a stable, reliable, flexible, efficient and economically implementable communication system is created, particularly for a motor vehicle.
Conventional FlexRay network nodes can naturally also be provided in the communication system in addition to the FlexRay network nodes configured according to the invention.
The FlexRay network nodes may naturally also be set up such that, in addition to the conversion of data onto the physical FlexRay layer according to the invention, the FlexRay network nodes may also carry out a conventional conversion of data onto the physical FlexRay layer, in which case the data may previously have been packaged in FlexRay data frames.
Within the scope of the invention, an IP data packet includes data packets formed according to the Internet protocol but also data packets that are derived from such an Internet-protocol-conformal data packet or are formed in conformity with such data packets according to the Internet protocol. For example, within the scope of the invention, an IP data packet also includes data packets which are formed according to the Internet protocol but which have further data, or parts of data packets which are formed according to the Internet protocol. Likewise, within the scope of the invention, the term “IP data packet” includes data packets which directly or indirectly originate from an Internet protocol layer. As a rule, the IP data packet has an IP address or destination address.
Depending on the embodiment, the FlexRay bus system and/or the FlexRay network nodes may be devices which are modified or “shed” with respect to a conventional FlexRay bus system and/or conventional FlexRay network nodes. Within the scope of the invention, a FlexRay network node therefore also includes network nodes which execute or comprise only the physical layer of a FlexRay protocol. Correspondingly, within the scope of the invention, a FlexRay bus system includes a bus system or bus protocol which only executes or comprises the physical layer of the FlexRay protocol. The other layers may be completely or partially executed according to other protocols or specifications that are, for example, known per se.
A communication system which includes an IP network and a FlexRay bus system is particularly flexible, in which case the IP network is coupled with the FlexRay bus system by way of a router.
By means of the adaptation layer, the contents of the bit positions of the data or data packets provided in the media-independent data format or data packet format are preferably each converted onto corresponding signals of the physical layer of the FlexRay bus system (FRB). In this case, the FlexRay network nodes are set up such that contents of the bit positions of the data or data packets in the media-independent data format or data packet format are converted particularly indirectly or directly in each case onto corresponding signals, signal shapes, pulse shapes or signal pulses of the physical layer of the FlexRay bus system (FRB).
The FlexRay bus system, particularly the physical layer of the FlexRay bus system, is preferably based on two physical FlexRay channels (first channel and second channel). For this purpose, a communication control device, the media access layer or the adaptation layer of at least one FlexRay network node is set up such that the physical layer of the FlexRay bus system includes a first and a second physical channel.
In addition, the communication control device, the media access layer or the adaptation layer is advantageously set up such that data are sent by way of the first channel and data are received by way of the second channel.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.